Because of their excellent heat resistance and ozone resistance, vulcanization products of ethylenepropylene.diene copolymers have been widely used as raw materials for the manufacture of automotive industry parts, industrial rubber products, electrical insulating materials, building industry products, rubber products such as rubber coated fabrics and plastic blending materials for polypropylene, polystyrene, etc. However, because the ethylene-propylene.diene copolymers are poor in resistance to dynamic fatigue, they were found to be unsuitable for specific uses, for example, rubber vibration insulator, rubber roll, belt, tire and covering materials for vibrating section.
U.S. Pat. No. 3,933,769, on the one hand, discloses vulcanizable copolymers low in gel content prepared by copolymerization in the presence of coordination catalyst of at least one monomer selected from 1-butene and .alpha.-olefins of 5-12 carbon atoms and mixtures of 5-methyl-1,4-hexadiene and 4-methyl-1,4-hexadiene (containing at least 15% of 5-methyl-1,4-hexadiene). U.S. Pat. No. 4,340,705 discloses sulfur-vulcanizable copolymers low in gel content prepared by copolymerization of monoolefins of 4-12 carbon atoms and non-conjugated .alpha.,.omega.-polyenes of from 8 to about 36 carbon atoms in the presence of catalyst systems prepared by the addition to transition metal compounds and organoaluminum compounds of hexaalkylphosphoric acid triamides or organophosphoric acid esters.
Incidentally, diene rubber such as natural rubber, isoprene rubber, SBR and BR is excellent in properties such as workability and strength and widely used as raw material for the manufacture of tire, automotive parts, general-purpose industrial parts, etc. However, diene rubber had such a disadvantage in that because the diene rubber is poor in weathering resistance and ozone resistance, the articles manufactured therefrom are short in product life.
U.S. Pat. No. 4,645,793 discloses blends of ethylene..alpha.-olefin copolymer rubber improved in weathering resistance and ozone resistance. However, such blends of ethylene..alpha.-olefin copolymer rubber had a disadvantage that they deteriorate in resistance to dynamic fatigue (flexural fatigue resistance) or in adhesion to fiber, though they are certainly improved in weathering resistance and ozone resistance.
Ethylene-.alpha.-olefin copolymer rubber typified by ethylene propylene diene copolymer rubber has been widely used for the manufacture of automotive parts, industrial rubber products, electrical insulating materials and building industry products because of its excellent strength characteristics, heat resistance and weathering resistance. However, because ethylene..alpha.-olefin copolymer rubber is poor in resistance to dynamic fatigue, vibration-damping properties and vibration-deadening properties, there was much room for further improvement when it is used for the manufacture of rubber vibration insulator, rubber roll, belt and tire.
On the one hand, though natural rubber is excellent in strength characteristics and resistance to dynamic fatigue, it is poor in heat resistance and weathering resistance, and also its vibration-damping properties and vibration-deadening properties cannot be said to be sufficient, and a further improvement from the practical viewpoint of these properties was desired.
The present invention is intended to solve such technical problems associated with the prior art, and an object of the invention is to provide novel higher .alpha.-olefin.non-conjugated diene copolymers that are sulfur-vulcanizable and substantially free from gel formation, processes for preparing the same, and to novel vulcanization products obtained from the higher .alpha.-olefin.non-conjugated diene copolymers, said vulcanization products being excellent in weathering resistance, ozone resistance, resistance to heat aging, low-temperature characteristics, vibration-damping properties and resistance to dynamic fatigue.
A further object of the invention is to provide vulcanizable rubber compositions excellent in workability, strength characteristics, weathering resistance, ozone resistance and resistance to dynamic fatigue and also excellent in adhesion to fiber.
Another object of the invention is to provide vulcanizable rubber compositions excellent in strength characteristics, heat resistance, weathering resistance, vibration-damping properties, vibration-deadening properties and resistance to dynamic fatigue.